A condition even more rare than hypoplastic left heart syndrome (HLHS) is known as hypoplastic right heart syndrome. In this condition, the infant will be born well-developed but with chambers, valves and related blood vessels on the right side of the heart so malformed that they cannot efficiently pump blood to the lungs.

These defects result in severely reduced oxygen-rich blood supply throughout the body, and the baby will have a bluish tint (cyanosis) to the skin, lips, fingernails and other parts of the body. Like HLHS, the treatment options include open-heart surgeries, heart transplant surgery or the Norwood procedure.